There are some great websites which provide sophisticated yet understandable answers to how nuclear weapons work, the history of their development and testing, and what effects these weapons have when detonated.
I do not wish to attempt to duplicate or paraphrase this material.
Please click on the highlighted URLs below to go to the best online explanations available.
General information and historical data about nuclear weapons
Detailed scientific explanations and observations of nuclear weapons
The Glasstone-Dolan book is considered the primary scientific reference on nuclear weapons and nuclear weapons effects. Listed below are the URLs for the third edition, published in 1977.